There are prior art techniques for encoding the channels of a multichannel audio system. An example of a multichannel audio system is a 5.1 channel system comprising a center channel (C), a left front channel (Lf), a right front channel (Rf), a left surround channel (Ls), a right surround channel (Rs), and a low frequency effects (Lfe) channel. An existing approach of coding such a system is to code the center channel C separately, and performing joint stereo coding of the front channels Lf and Rf, and joint stereo coding of the surround channels Ls and Rs. The Lfe channel is also coded separately and will in the following always be assumed to be coded separately.
The existing approach has several drawbacks. For example, consider a situation when the Lf and the Ls channel comprise a similar audio signal of similar volume. Such an audio signal will sound as if comes from a virtual sound source being located between the Lf and the Ls speaker. However, the above described approach is not able to efficiently code such an audio signal since it prescribes that the Lf channel is to be coded with the Rf channel, instead of performing a joint coding of the Lf and the Ls channel. Thus the similarities between the audio signals of the Lf and Ls speaker cannot be exploited in order to achieve an efficient coding.
There is thus a need for an encoding/decoding framework which has an increased flexibility when it comes to coding of multichannel systems.